DAO Enzyme Deficiency

What is Diamine Oxidase (DAO)?

Diamine Oxidase (DAO) is an enzyme involved in the metabolism and inactivation of histamine. Previously called “histaminase,” DAO is found primarily in the digestive tract.

DAO is the most important enzyme in the body for managing histamine. It is primarily found in the cell tissue of the intestinal mucosa and the kidneys. DAO works by breaking down histamine through a process called oxidative deamination. The DAO reacts with histamine, breaking it down into the byproducts before it can pass into the bloodstream. The byproducts are then flushed from the system through urination. DAO is also active within the liver, where it helps to control the amount of histamine that enters circulation.

In healthy adults, DAO breaks down histamine either contained in or released by common foods. However, everyone has different levels of DAO and DAO activity. When DAO levels and DAO activity are low, histamine can quickly surpass the point at which the body can readily process it. When this occurs, the body may signal that it is experiencing a histamine overload.